17 – Averages

Why Should I Care?

You can make numbers tell the story you wish to tell. This is unethical and evil. So knowing how others are – or not – using basic tricks of statistics will help you read through the lies.

Definitions

Central tendency

 

Frequency

 

Mean

 

Median

 

Mode

Skewed distributions

If the average grade in your RM class is 58%, but the median and mode are 75%, would you say most people are doing well?

In this case, the mean is _________________ the central tendency.

If the average grade in your RM class is 88%, but the median and mode are 65%, would you say most people are doing well?

In this case, the mean is _________________ the central tendency.

Multimodal distributions

Unimodal

Multimodal

 

AVERAGES

Students handed in their third RM assignment, and here are the results (on 50 pts).

Use the data below to calculate the mean, the median and the mode of the distribution.

• Is the distribution normal or skewed?
• If you were in this class, would you prefer to score over the mean, or over the median?

Student	Grade - Assignment 3		Score	Frequency
1	20		0
2	48		5
3	22		17
4	50		18
5	37		20
6	47		22
7	36		28
8	17		29
9	39		30
10	42		32
11	33		33
12	18		34
13	18		35
14	29		36
15	5		37
16	42		39
17	32		41
18	28		42
19	0		43
20	30		46
21	41		47
22	35		48
23	37		50
24	41
25	46
26	34
27	41
28	42
29	43
30	47

MEAN             =          sum / n                         =

MODE             =          highest frequency           =

MEDIAN         =          middle value                 =